title: [Biopharmaceutical studies of similar theophylline products in the national market].
abstract: BACKGROUND
  Theophylline has a narrow therapeutic margin, therefore it should be formulated as a sustained release pharmaceutical form. In Chile there are several brands of sustained release theophylline forms that have not been tested.
  
  
  OBJECTIVE
  To perform in vitro release-dissolution studies of sustained release theophylline forms commercialized in Chile.
  
  
  METHODS
  Five sustained release products were studied according to the specifications of the seventh supplement of The United States Pharmacopoeia Convention. Release and dissolution rates were compared with a rapid release aminophylline form. The identity, validation and active principle content of each product was also studied.
  
  
  RESULTS
  All the studied forms complied with the quality requirements of the USP XII. The dissolution rate constants of the products at pH 6 ranged from 0.0583 to 0.2130, compared with 7.1 for the rapid release form. The dissolution of all products, except one, was pH dependent.
  
  
  CONCLUSIONS
  These results underscore the need to systematically study the quality of pharmaceutical products, considered similar, whose differences could have potential risks for patients.
authors.affiliation: Pontificia Universidad Católica de Chile, Facultad de Química, Departamento de Farmacia, Vicuña Mackenna, Santiago.
authors.forename: R
authors.initials: R
authors.lastname: Pezoa
authors.forename: A M
authors.initials: AM
authors.lastname: Concha
authors.forename: M
authors.initials: M
authors.lastname: Ramírez
authors.forename: J
authors.initials: J
authors.lastname: Alvarez
mesh_terms: D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D013806:Theophylline / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D001993:Bronchodilator Agents; D013806:Theophylline
vernacular_title: Estudios biofarmacéuticos de productos similares de teofilina del mercado nacional.